BASIS OF PRESENTATION AND ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 30, 2025	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Sep. 26, 2025	Dec. 31, 2024
Temporary Equity [Line Items]
Deferred offering costs		$ 6,724		$ 6,724			$ 0
Loss on issuance of convertible preferred stock		$ 355,551	$ 0	355,551	$ 0
Warrants issued to purchase common stock (in shares)						2,552,467
Aggregate grant date fair value, warrants						$ 67,236
GE Aerospace
Temporary Equity [Line Items]
Exercise price, warrants (in dollars per share)						$ 0.01
Warrant expense				$ 308
Class A common stock | Subsequent Event
Temporary Equity [Line Items]
Reduction of carrying value	$ 10,723
Convertible Series C and C-1 preferred stock
Temporary Equity [Line Items]
Convertible preferred stock, purchase price (in dollars per share)		$ 114.47		$ 114.47
Minimum | Convertible Series C and C-1 preferred stock
Temporary Equity [Line Items]
Convertible preferred stock, fair value range (in dollars per share)		114.47
Maximum | Convertible Series C and C-1 preferred stock
Temporary Equity [Line Items]
Convertible preferred stock, fair value range (in dollars per share)		$ 196.73